In an evolved-universal terrestrial radio access network (E-UTRAN), a service known as multimedia broadcast/multicast service (MBMS) has been studied.
The MBMS is a broadcast/multicast service using a mobile packet network. In a previous video content distribution service, content is transmitted in a circuit switching (CS) area, a point-to-point connection is established between a server and each user who receives the service, and the content is provided by streaming.
However, in the case in which a multimedia service is simultaneously provided to a number of users, a multicast service is necessary. A service in which a multicast connection is established in a packet switching (PS) area is the MBMS, and the use of a point-to-multipoint type radio channel has been studied.
In the MBMS, the use of any one or both of a unicast/MBMS mixed cell and an MBMS dedicated cell has been studied.
The unicast/MBMS mixed cell uses a frequency band to be used along with a service other than the MBMS. The MBMS dedicated cell uses an MBMS dedicated frequency band.
In any case, implementation by a single frequency network (SFN) is possible in MBMS transmission. This is called an MBMB SFN (multimedia broadcast single frequency network (MBSFN)).
In the case of the unicast/MBMS mixed cell, an MBMS subframe (multicast CH (MCH) subframe) and a unicast subframe is subjected to time division multiplexing (TDM), so that MBMS transmission is performed, as shown in Patent Document 1.
In this case, a radio reception device transmits a unicast frame and an MBMS frame by TDM as disclosed in Patent Document 1. Thus, a unicast channel, a unique pilot channel, and the like are derived in a unicast frame period. Also, an MBMS channel and a common pilot channel (and a unique pilot channel) are derived in an MBMS frame period. MBMS and unicast data are received by demodulating each data.
On the other hand, the MBMS dedicated cell has also been studied as disclosed in Non-Patent Document 1. In the MBMS service, no unicast data is transmitted and there is no operation which responds to an uplink signal.
During MBMS reception in the MBMS dedicated cell, the radio reception device can not perform unicast communication. Thus, a unicast signal reception method performs communication by a system, not by E-UTRA.
Even when an E-UTRA service is provided in the same area, a prescription for simultaneously using the MBMS and the unicast service does not exist. Thus, it is necessary to provide a unicast communication system, separated from a reception system for receiving the MBMS, as in other systems.
Patent Document 2 discloses a method of transmitting the unicast service and the MBMS by frequency division multiplexing (FDM).
If some subcarriers are exclusively used for the MBMS, the same process as that of a receiver disclosed in Patent Document 1 is performed. That is, if the MBMS is serviced, MBMS data is received. If the unicast service is received, unicast data is received.
However, it is necessary to provide a dedicated radio reception device for multicast communication in an area where a multicast communication service such as the MBMS is provided in the related art. Thus, there is a problem in that multicast communication and unicast communication can not be simultaneously performed between a radio transmission device and a radio reception device.
Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2007-300503
Patent Document 2: Japanese Unexamined Patent Application, First Publication No. 2007-194867
Non-Patent Document 1: 3 GPP TS 36.300 V8.2.0 (2007-09); 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 (Release 8)